Oil, in general, does not lose its lubricating properties with use. It does, however, become contaminated. It often then is considered unfit for further lubricating use and may be disposed of as waste oil.
In address of this problem, U.S. Pat. No. 5,820,748 to Shadikhan discloses safe removal of gasses, water and solvents from used lubricating oils with vacuum apparatus under mild temperature conditions. Removal of solids can be assisted by use of a coagulant. As effective as the technology of that disclosure is, improvements to the art would be welcome.